The Panel of Reactive Antibodies (PRA) is a test panel used to measure the patient reactivity to human leukocyte cell antigens (HLA). A PRA of 75% means the patient reacted to 75% of the antigens on the panel. A high PRA indicates that the subject already has antibodies and is highly SENSITIZED. Spontaneous decreases in PRA titers rarely occur. Thus the probability of transplantation in sensitized patients is significantly decreased.